Presence Of Thiophenol Research Articles

Electrochemical Direct Synthesis of N-Sulfenylimines from Amines in the Presence of Thiophenols.

N-Sulfenylimines are important molecules owing to their value in organic synthesis. Herein, we developed an electrochemical oxidative cross-coupling reaction between amines and thiols to synthesize N-sulfenylimines without a transition-metal catalyst and external oxidant. Various amines and thiols were compatible, generating the desired products in up to 86% yield.

Mild solvothermal syntheses and crystal structures of two quaternary hetero-transition metal sulfides RbAg5HgS4 and CsAgHgS2

Two quaternary hetero-transition metal sulfides RbAg5HgS4 (1) and CsAgHgS2 (2) have been successfully synthesized under mild solvothermal method in the presence of thiophenol as a mineralizer. Compound 1 features an interesting 3-D [Ag5HgS4]- framework composed of 16-membered ring [Ag (2)4M(1)4S8] (M ​= ​Ag/Hg) and quasi-8-membered ring [Ag (2)4S4] which are all constructed by MS2 and AgS2 linear units. Compound 2 possesses anionic [AgHgS2]nn− layers formed with MS4 (M ​= ​Ag/Hg) tetrahedra, in which Ag+ and Hg2+ ions occupy the same crystallographic site. Particularly, this is the first time that quaternary A-Ag-Hg-S (A ​= ​alkali metal) system were explored via solvothermal method, which demonstrates that structural directing agents have significant influence on the structures of hetero-transition metal sulfides. Furthermore, the XRD experiment and band gap value of compound 2 were also investigated.

A photosensitized metal free approach to α‐ketoamides:sequential oxidative amidationdiketonization of terminal alkynes

AbstractA novel transition metal‐free photosensitized protocol has been developed for the synthesis of α‐ketoamides via oxidative coupling of alkynes and amines in the presence of thiophenol under visible light irradiation and rose bengal dye. A series of alkynes with both electron‐donating and electron‐withdrawing groups were successfully employed for the synthesis of their corresponding α‐ketoamides. This reaction presents a benign visible light based milder synthetic methodology with broad functional‐group tolerance.

Design and Synthesis of a Fluorescent Probe with a Large Stokes Shift for Detecting Thiophenols and Its Application in Water Samples and Living Cells.

A turn-on florescent probe (probe-KCP) was developed for highly selective detection of thiophenols based on a donor-excited photo-induced electron transfer mechanism. Herein, the synthesis of the probe, a chalcone derivative, through a simple straightforward combination of a carbazole-chalcone fluorophore with a 2,4-dinitrophenyl functional group. In a kinetic study of the probe-KCP for thiophenols, the probe displayed a short response time (~30 min) and significant fluorescence enhancement. In selection and competition experiments, the probe-KCP exhibited excellent selectivity for thiophenols over glutathione (GSH), cysteine (Cys), sodium hydrosulfide (NaSH), and ethanethiol (C2H5SH) in addition to common anions and metal ions. Using the designed probe, we successfully monitored and quantified thiophenols, which are highly toxic. This turn-on fluorescence probe features a remarkably large Stokes shift (130 nm) and a short response time (30 min), and it is highly selective and sensitive (~160-fold) in the detection of thiophenols, with marked fluorescence in the presence of thiophenols. probe-KCP responds to thiophenols with a good range of linearity (0–15 μM) and a detection limit of 28 nM (R2 = 0.9946) over other tested species mentioned including aliphatic thiols, thiophenol analogues, common anions, and metal ions. The potential applications of this carbazole-chalcone fluorescent probe was successfully used to determine of thiophenols in real water samples and living cells with good performance and low cytotoxicity. Therefore, this probe has great potential application in environment and biological samples.

Solid-phase synthesis of homodetic cyclic peptides from Fmoc-MeDbz-resin

Cyclic homodetic peptides are very appealing for medicinal chemistry programs. In addition to the high efficiency and selectivity inherently associated with peptides, a cyclic structure totally formed by amide bonds increases their stability under physiological conditions. Here Fmoc-MeDbz-resin was studied for the preparation of these peptides. Our results demonstrate the usefulness of this strategy for the preparation of cyclic “head-to-side chain” peptides through cyclative cleavage (simultaneous cyclization and release from the resin). In contrast, for the synthesis of the “head-to-tail” counterparts, the cyclization-cleavage should be carried out in the presence of thiophenol.

Computational Kinetic Modeling of the Catalytic Cycle of Glutathione Peroxidase Nanomimic: Effect of Nucleophilicity of Thiols on the Catalytic Activity.

The catalytic cycle of a new derivative of ebselen, 1, was elucidated via three steps by the density functional theory and solvent-assisted proton exchange procedure involving indirect proton exchange through a hydrogen-bonded transfer network. Different behaviors of the aromatic and aliphatic thiols were investigated in the reduction of selenoxide (step 2 → 3) and selenurane (step 3 → 1) based on their nucleophilicity. The reduction of selenoxide in the presence of thiophenol (ΔG‡ = 15.9 kcal·mol-1) is faster than that of methanethiol (ΔG‡ = 29.3 kcal·mol-1), and methanethiol makes the reduction of selenoxide unspontaneous and kinetically unfavorable (ΔG = 2.8 kcal·mol-1). The nucleophilic attack may be enhanced by using the thiophenol backbone at the selenium center to lower the energy barrier of the selenoxide reduction (ΔG‡ = 15.9 kcal·mol-1). On the basis of the turnover frequency calculations, during the catalytic cycle, the rate of the reaction was analyzed and discussed. Low values of the electron density and Laplacian at the transition states are the evidence of the covalent O-H and O-O bonds rupture in the presence of methanethiol and thiophenol. The nature of the critical bond points was characterized, using the quantum theory of atoms in molecules, based on the electron location function and localized orbital locator values. Finally, the charge transfer process at the rate-determining step was investigated based on the natural bond orbital analysis.

ChemInform Abstract: NaBH3CN and Other Systems as Substitutes of Tin and Silicon Hydrides in the Light or Heat‐Initiated Reduction of Halosugars: A Tunable Access to Either 2‐Deoxy Sugar or 1,5‐Anhydro‐itols.

AbstractThe access to the title compounds depends on the leak or the presence of thiophenol.

In Search of Catalytic Antioxidants—(Alkyltelluro)phenols, (Alkyltelluro)resorcinols, and Bis(alkyltelluro)phenols

The quenching of peroxyl radicals by ortho-(alkyltelluro)phenols occurs by a more complex mechanism than formal H-atom transfer. In an effort to improve on this concept, we have prepared (alkyltelluro)resorcinols and bis(alkyltelluro)phenols and evaluated their catalytic chain-breaking and preventive antioxidative properties. The in situ formed trianion produced from 2-bromophenol and 3 equiv of tert-butyllithium was allowed to react with dialkyl ditellurides to provide ortho-(alkyltelluro)phenols in low yields. 2-Bromoresorcinols after treatment with 4 equiv of tert-butyllithium similarly afforded 2-(alkyltelluro)resorcinols. Bis(alkyltelluro)phenols were accessed by allowing the trianion produced from the reaction of 2,6-dibromophenol with 5 equiv of tert-butyllithium to react with dialkyl ditellurides. The novel phenolic compounds were found to inhibit azo-initiated peroxidation of linoleic acid much more efficiently than α-tocopherol in a two-phase peroxidation system containing excess N-acetylcysteine as a stoichiometric thiol reducing agent in the aqueous phase. Whereas most of the (alkyltelluro)phenols and resorcinols could inhibit peroxidation for only 89-228 min, some of the bis(alkyltelluro)phenols were more regenerable and offered protection for >410 min. The novel (alkyltelluro)phenols were also evaluated for their capacity to catalyze reduction of hydrogen peroxide in the presence of thiophenol (glutathione peroxidase-like activity). (Alkyltelluro)resorcinols 7a-c were the most efficient catalysts with activities circa 65 times higher than those recorded for diphenyl diselenide.

Manganese Doped Cadmium Sulphide (CdS: Mn) quantum Particles: Topological, photoluminescence And Magnetic Studies

Nano-polycrystalline samples of cadmium sulphide doped with 0, 2, 4, 6, 8 and 10 atomic % of Mn were prepared by a template based chemical route. The presence of thiophenol as template on the surface of the samples has been detected with FTIR technique. Particle sizes of 15-50 nm range, hexagonal structure and polycrystalline nature of the samples have been identified through SEM and TEM techniques. Surface states in the band gap region of the samples confirmed by PL study also revealed that the size of the particles is in the nano range. The low temperature magnetization study suggested the 10 at.% Mn doped sample might be in a re-entrant-spin glass phase at 77 K. Copyright © 2013 VBRI press.

ChemInform Abstract: Solvothermal Synthesis and Characterization of One‐Dimensional Indium Polyselenides with Transition Metal Complexes.

AbstractThe presence of thiophenol appears to be essential in the synthesis of the indium selenide (III).

Light-Triggered Ruthenium-Catalyzed Allylcarbamate Cleavage in Biological Environments

The sandwich complex [Cp*Ru(η6-pyrene)]PF6 (Cp* = η5-C5(CH3)5) serves as a photoactivatable catalyst for the conversion of N-allylcarbamates into their amines in the presence of thiophenol under bi...

A novel fluorogenic hybrid material for selective sensing of thiophenols

A fluorogenic organic-inorganic hybrid sensory material (denoted as material III) was successfully prepared by immobilizing disulfide-based receptors within the channels of mesoporous silica MCM-41. The material showed high sensitivity and excellent selectivity towards thiophenols due to appropriate combination of the stronger nucleophilicity of thiophenols and the secondary interactions (hydrophobicity and π–π stacking interactions) provided by the inorganic support. Fluorescence measurements revealed that the emission intensity of material III increased significantly upon addition of thiophenols, while it was not observed for aliphatic thiols and other nucleophiles. The detection limit of this material to p-toluenethiol was estimated to be 7.4 × 10−6 M, and a good linear relationship between the fluorescence intensity and p-toluenethiol concentration (in the range of 0–110 μM) was achieved. The pronounced emission enhancement could be attributed to the following conversion process: a coumarin derivative is released from material III by cleaving the disulfide bonds in the presence of thiophenols, and then oxidized spontaneously to a fluorescent dye (coumarin 6) under ambient conditions. This novel sensing method viadisulfide-based groups as the active site combining with the synergistic effect provided by the inorganic support is expected to open a new avenue for thiophenols sensing.

ChemInform Abstract: Oxygenation of γ,δ-Unsaturated Ketones in the Presence of Thiophenol. Efficient Formation of Cyclic Peroxides.

Abstract γ,δ-Unsaturated ketones were found to be oxygenated in the presence of thiophenol to give the corresponding cyclic peroxides. The electrochemical initiation accelerated the reaction markedly.

ChemInform Abstract: Electroinitiated Oxygenation of Alkenyl Sulfides and Alkynes in the Presence of Thiophenol.

Electrolysis of alkenyl sulfides in the presence of thiophenol with bubbling of molecular oxygen gave the corresponding α-(phenylthio) carbonyl compounds with the consumption of a catalytic amount of electricity. An electroinitiated radical chain mechanism has been proposed. The reaction also took place without electrochemical initiation, but much (5-50 times) longer reaction time was required for the completion of the reaction. The potential utility of the present reaction in organic synthesis is demonstrated by the net 1,2-transposition of a phenylthio group and a carbonyl group. The electroinitiated oxygenation of ketene dithioacetals also proceeded smoothly to give the corresponding α-(phenylthio) thiol esters. It was also found that the electroinitiated oxygenation of alkynes in the presence of thiophenol gave α-(phenylthio) carbonyl compounds. A mechanism involving the initial formation of alkenyl sulfides has been proposed

New pterocarpanquinones: Synthesis, antineoplasic activity on cultured human malignant cell lines and TNF-α modulation in human PBMC cells

A new pterocarpanquinone (5a) was synthesized through a palladium catalyzed oxyarylation reaction and was transformed, through electrophilic substitution reaction, into derivatives 5b–d. These compounds showed to be active against human leukemic cell lines and human lung cancer cell lines. Even multidrug resistant cells were sensitive to 5a, which presented low toxicity toward peripheral blood mononuclear cells (PBMC) cells and decreased the production of TNF-α by these cells. In the laboratory these pterocarpanquinones were reduced by sodium dithionite in the presence of thiophenol at physiological pH, as NAD(P)H quinone oxidoredutase-1 (NQO1) catalyzed two-electron reduction, and the resulting hydroquinone undergo structural rearrangements, leading to the formation of Michael acceptors, which were intercepted as adducts of thiophenol. These results suggest that these compounds could be activated by bioreduction.

Syntheses and Characterization of a Series of Silver−Thioantimonates(III) and Thioarsenates(III) Containing Two Types of Silver−Sulfur Chains

Three framework silver-thioantimonates, K(3)Ag(9)Sb(4)S(12)(1), Rb(3)Ag(9)Sb(4)S(12)(2), and Cs(3)Ag(9)Sb(4)S(12)(3), and one layered silver-thioarsenate, CsAg(2)AsS(3)(4), have been synthesized solvothermally in the presence of thiophenol as a mineralizer. Compounds 1, 2, and 3 are isostructural and contain infinite silver-sulfur chains [Ag(9)S(12)](15-). These chains are connected to one another by the antimony atoms to generate wide channels along the [001] direction where the alkali metal cations reside. The structure of 4 consists of helical chains [Ag(2)S(3)](4-) linked by the arsenic atoms to form layers with potassium ions between the layers.

Solvothermal Syntheses of Two Novel Layered Quaternary Silver−Antimony(III) Sulfides with Different Strategies

Two new silver antimony sulfides, KAg2SbS3 (1) and K2Ag3Sb3S7 (2), have been synthesized solvothermally in the presence of thiophenol as a mineralizer. Compound 1 contains a hexagonal net formed by condensation of Ag2SbS3 six-membered rings. These sheets are linked through Ag−S bonds to obtain double layers. The structure of 2 consists of infinite [Sb2S4]2− chains and [Ag6Sb2S10]∞8− columns linked to form layers. The [Sb2S4]∞2− chains are generated by vertex-shared SbS33− pyramids, while [Ag6Sb2S10]∞8− columns are composed of edge-shared of SbS3 pyramid, AgS3 triangles, and a AgS4 tetrahedron, and contain a Ag3SbS3 semicube. The optical band gaps of the two compounds are 2.1 and 2.2 eV, respectively.

Thio-mediated two-component coupling reaction of carboxylic acids and isonitriles under mild conditions

The coupling reaction between carboxylic acids and isonitriles in the presence of thiophenol as activator under mild conditions is described.

Effect of thiophenol on thermal fragmentation of polyisoprene

As a fundamental study for chemical recycle of waste vulcanized rubber to reproduce functional polymers, polyisoprene (PI) was thermally fragmented to obtain low molecular weight PI in the presence of thiophenol (PhSH). PI (Mw = 51,000) was heated at 140°C under air atmosphere to give low molecular weight PI. The fragmentation in the presence of PhSH effectively decreased the molecular weight (Mw = 7400), which is significantly lower than that in the fragmentation in the absence of PhSH. The fragmented PI contained phenyl sulfide moieties based on the addition of phenyl thiyl radical to the hydrogen abstracted methylene or the double bond moieties. Tgs of the fragmented polymers were higher than that of the original PI, despite the lower molecular weights, probably because of the introduction of the rigid phenyl sulfide moieties and the terminal polar carbonyl groups formed by oxidation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007

Antioxidant Profile of Ethoxyquin and Some of Its S, Se, and Te Analogues

6-(Ethylthio)-, 6-(ethylseleno)-, and 6-(ethyltelluro)-2,2,4-trimethyl-1,2-dihydroquinoline-three heavier chalcogen analogues of ethoxyquin-were prepared by dilithiation of the corresponding 6-bromodihydroquinoline followed either by treatment with the corresponding diethyl dichalcogenide (sulfur derivative) or by insertion of selenium/tellurium into the carbon-lithium bond, oxidation to a diaryl dichalcogenide, borohydride reduction, and finally alkylation of the resulting areneselenolate/arenetellurolate. Ethoxyquin, its heavier chalcogen analogues, and the corresponding 6-PhS, 6-PhSe, and 6-PhTe derivatives were assayed for both their chain-breaking antioxidative capacity and their ability to catalyze reduction of hydrogen peroxide in the presence of a stoichiometric amount of a thiol reducing agent (thiol peroxidase activity). Ethoxyquin itself turned out to be the best inhibitor of azo-initiated peroxidation of linoleic acid in a water/chlorobenzene two-phase system. In the absence of N-acetylcysteine as a coantioxidant in the aqueous phase, it inhibited peroxidation as efficiently as alpha-tocopherol but with a more than 2-fold longer inhibition time. In the presence of 0.25 mM coantioxidant in the aqueous phase, the inhibition time was further increased by almost a factor of 2. This is probably due to thiol-mediated regeneration of the active antioxidant across the lipid-aqueous interphase. The ethyltelluro analogue 1d of ethoxyquin was a similarly efficient quencher of peroxyl radicals compared to the parent in the two-phase system, but less regenerable. Ethoxyquin was found to inhibit azo-initiated oxidation of styrene in the homogeneous phase (chlorobenzene) almost as efficiently (kinh = (2.0 +/- 0.2) x 106 M-1 s-1) as alpha-tocopherol with a stoichiometric factor n = 2.2 +/- 0.1. At the end of the inhibition period, autoxidation was additionally retarded, probably by ethoxyquin nitroxide formed during the course of peroxidation. The N-H bond dissociation enthalpy of ethoxyquin (81.3 +/- 0.3 kcal/mol) was determined by a radical equilibration method using 2,6-dimethoxyphenol and 2,6-di-tert-butyl-4-methylphenol as equilibration partners. Among the investigated compounds, only the tellurium analogues 1d and, less efficiently, 1g had a capacity to catalyze reduction of hydrogen peroxide in the presence of thiophenol. Therefore, analogue 1d is the only antioxidant which is multifunctional (chain-breaking and preventive) in character and which can act in a truly catalytic fashion to decompose both peroxyl radicals and organic hydroperoxides in the presence of suitable thiol reducing agents.